THEORETICAL INVESTIGATION ON AERODYNAMIC FORCE MEASUREMENT INTERFERED BY STRUCTURAL VIBRATIONS IN LARGE SHOCK TUNNEL

Structural vibration of aerodynamic measurement system is caused by the impulse forces generated by startup process of the shock tunnel, and the test time is too short to allow the vibration to decay. Therefore, the aerodynamic force measurement can be considered as a dynamic process, during which the signals outputted by balance are consist of aerodynamic force signals and vibration signals. Existing methods are lack of support of theory and the accuracies of them are limited. Theoretical analysis is used in this paper and we obtain the analytical solutions of fundamental characteristics of free vibrations and forced vibrations. Study of free vibrations focuses on the disciplines of aerodynamic force measurement interfered by a single vibration shape and amplitude of interference changed with section of force measurement. The inferences of di erent vibration shapes during forced vibration motivated by varied forces are investigated in research of forced vibration. Results show that there are theoretical defects for traditional acceleration compensation techniques because the zero points of amplitude of interference and acceleration are inconsistent. What's more, the influences of section for force measurement, acting position of force and type of force should be considered to determine the main source of interference in experiments.